Scala - NULL handling with MAP

Sharing three useful types that express a very useful concept i learned today, for NULL handling.

Most languages have a special keyword or type instance that’s assigned to reference variables when there’s nothing else for them to refer to. In Java, it’s null, which is a keyword, not an instance of a type. Thus, it’s illegal to call any methods on it. But this is a confusing choice on the language designer’s part. Why return a keyword when the programmer expects an instance of a type? 

Of course, the real problem is that null is a giant source of nasty bugs. What null really signals is that we don’t have a value in a given situation. If the value is not null, we do have a value. Why not express this situation explicitly with the type system and exploit type checking to avoid NullPointerExceptions? 

Option - lets us express this situation explicitly without the null “hack.” Option is an abstract class and its two concrete subclasses are 

1. Some, for when we have a value, and 
2. None, when we don’t. 

If the Option is a Some, Some.get returns the value. However, if the Option is actually None, then None.get throws a NoSuchElementException, in this case need to handle with safer alternative getOrElse

In action with Scala worksheet

val stateCapitals = Map( 

"Alabama" -> "Montgomery", 

"Alaska" -> "Juneau", 

"Wyoming" -> "Cheyenne") 

println( "Get the capitals wrapped in Options:" ) 

println( "Alabama: " + stateCapitals.get("Alabama") ) 

println( "Wyoming: " + stateCapitals.get("Wyoming") ) 

println( "Unknown: " + stateCapitals.get("Unknown") ) 

println( "Get the capitals themselves out of the Options:" ) 

println( "Alabama: " + stateCapitals.get("Alabama").get ) 

println( "Wyoming: " + stateCapitals.get("Wyoming").getOrElse("Oops!") ) 

println( "Unknown: " + stateCapitals.get("Unknown").getOrElse("Oops2!") ) 

Output

Get the capitals wrapped in Options:

Alabama: Some(Montgomery)

Wyoming: Some(Cheyenne)

Unknown: None

Get the capitals themselves out of the Options:

Alabama: Montgomery

Wyoming: Cheyenne

Unknown: Oops2!